Still battling: Gary McKinnon with mother Janis Sharp, who will be waiting to hear what the Home Secretary has to say after the meeting

Senior MPs will step up the pressure on Alan Johnson to halt the extradition of Gary McKinnon at a key meeting in Westminster today.

A cross-party delegation will warn the Home Secretary that he has a legal duty to stop the 43-year-old Asperger's sufferer being sent to the U.S., where he faces 60 years in jail for computer hacking.

Michael Meacher, David Davis and Chris Huhne will call into question Mr Johnson's claims that he is powerless to prevent the controversial extradition.

They will highlight evidence from at least three senior lawyers who say Mr Johnson does have the power to ensure that Gary is tried in Britain.

The Mail is campaigning to save him from extradition on charges that he hacked into Nasa and Pentagon computers.

Mr Johnson was accused of presiding over a cover-up earlier this week after refusing to release crucial legal papers in the McKinnon case following a freedom of information request by the Mail.

Labour MP Mr Meacher said: 'Not only has the Home Secretary got the power but he has the duty to intervene in an extradition case even after the court process has ended if there is a real risk of a human rights breach should extradition proceed.

'Gary's medical condition is such that medical experts have concluded there is a grave risk to his health if he is extradited to the U.S.

'There is no reason why he cannot face charges in the UK for an act which took place in the UK.'

The Daily Mail's campaign started on July 3 with this headline story

Liberal Democrat home affairs spokesman Mr Huhne added: 'It is a good sign that he (Mr Johnson) is prepared to meet with us.

'We will be appealing to his better nature and ask him to take into account the fact that this is a vulnerable British citizen who can be tried in this country rather than the U.S.

'We will also be raising the issue of the conflicting legal advice.

'A string of independent legal counsel have issued clear legal advice that he can be tried here, but the Home Office claims otherwise.'

In July, two High Court judges ruled that they could not stop the Government from sending Gary to the U.S.

A headline from the Daily Mail's August 1 story

But, in a pointed statement, they said that if extradited 'his mental health will suffer and there are risks of worse, including suicide'.

Crucially, the judges also said Gary could be prosecuted in London - which would halt extradition.

Gary's mother Janis Sharp said: 'It is great news that such senior and serious politicians are able to meet with Alan Johnson to forward Gary's case. I will be outside the Home Office after the meeting to see what the Home Secretary has to say.

'We know, and independent lawyers know, that he has the power to stop Gary being sent to the United States.'

But sources close to Mr Johnson said: 'He has had a request from Michael Meacher to meet him. He is a parliamentary colleague and it is normal protocol for the Home Secretary to meet with colleagues and discuss issues which concern them.

'But nothing has changed. The court judgment is clear that it would be illegal for the Home Secretary to intervene in the extradition of Gary McKinnon.'